


Constructive Interference

by SStar



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Accidental Voyeurism, Anal Sex, Bathtub Sex, Bubble Bath, Established Relationship, M/M, Masturbation, POV Andrea, Plot What Plot/Porn Without Plot, Sibling Incest, Sibling Love, Voyeurism, holmescest
Language: English
Status: Completed
Published: 2014-06-02
Updated: 2014-06-02
Packaged: 2018-02-03 05:10:17
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,620
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1732352
Author URL: https://archiveofourown.org/users/SStar/pseuds/SStar
Summary: <blockquote class="userstuff">
              <p>Andrea (Anthea) discovers the relationship with Mycroft and Sherlock when she finds out the security cameras in the bedroom and bathrooms have been accidently activated.</p><p>She's sure incest shouldn't be <i>this</i> hot.</p>
            </blockquote>





	Constructive Interference

**Author's Note:**

  * For [scriggly](https://archiveofourown.org/users/scriggly/gifts).



> Disclaimer: all characters belong to ACD, Moffat, Gatiss and the BBC. I own nothing but my filthy mind.
> 
> Unbeta'd and un-edited I'm afraid - all mistakes are my very own.
> 
> Title is a physics reference.   
>  
> 
> For **scriggly** who so kindly gave to us all [And The Fever When I'm Beside Him](http://archiveofourown.org/works/1169171). Thank you and I hope you like this!

_Kitchen. Kitchen door. Gym. Upstairs hallway. Bathroom. Study._

Her finger stutters on the keyboard as her brain tries to catch up with her eyes. Andrea hits the key to take her back through the security cameras until comes back to the feed from the bathroom. A few moments later and she confirms the cameras in all the rooms are active.

In Mycroft Holme’s home.

She swears under her breath as she picks up her Blackberry, scrolls through her extensive list of contacts until she finds the team that handles their internal security. She flicks lazily between the feeds as she waits for her call to connect through to the team.

“Hello. Identification code?”

Andrea rattles off the code she memorised when she formally began working for Mycroft.

“Confirmed. How can I help?”

“I’m reviewing Mr Holmes’ surveillance and have found an error in the system.”

“Can you give me some more details?”

“The feeds to the bedrooms and bathrooms have been reinstated.”

“And that’s not in line with requirements?”

Andrea rolls her eyes. “Of course, how would you like surveillance in your bedrooms and bathrooms?” she rebukes the technician at the end of the line. “Bring up his specifications and tell me how this could have happened.”

There’s a long pause where she hopes the tech has some semblance of competence and sense. She flicks her eyes back to her computer monitor – the empty bathroom – tastefully decorated in warm sandstone, white and chrome and screaming decadence and comfort.

Not that she expected anything less of Mycroft Holmes.

“Ah, I see what’s happened.”

She can’t help the slight prissiness in her voice when she has to prompt for the explanation. “Wonderful. And that is?”

“Oh, right. Yes. Well it seems a routine maintenance cycle was running when a power-overload our end caused the entire system to reboot which set the cameras back to their original settings. All displays are green at our end; your office and the house itself are the only two locations with the direct feeds as you know.”

“So how can I change the settings back to how they were?”

“I can put the order in if you give me the camera serial numbers.”

“Fine,” she says as she taps her mouse through a series of folders until she finds the file she wants. She rattles off a set of serial numbers as soon as the file opens over the video feed. “How soon before the cameras are disabled?”

“Tomorrow lunchtime.”

“That long?”

“Yes. It’s not a good idea to run the maintenance cycles at night when clients are at home.”

“Makes sense I suppose,” Andrea admits grudgingly although that doesn’t help her immediate problem. “Can you disable the recording on those cameras only?”

“Sure thing ma’am.”

Andrea gritted her teeth for a moment. She wasn’t _old_ enough to be called _ma’am_ in her considered opinion. “You can do it now?”

“Yep.”

“Well then, please do.”

“Oh, okay.” There’s another pause where Andrea finds she has to stop herself from tapping her fingers on her desk. A clear sign of impatience that one should never show in front of others lest they use it against her. “That’s all done now.”

“Wonderful.”

“Is there anything else I can help you with today?”

“No,” Andrea replies quickly. Too quickly perhaps. “Thank you.”

She disconnects the line with one hand, while her other is back at her mouse as she focusses on her screen, closing down the now-redundant file and folders. She’s about to click on the email notification that pops up in the corner of her screen – a confirmation of the surveillance protocol changes no doubt – when she’s distracted by a movement on her screen.

It takes her a few seconds to realise what she’s looking at.

Sherlock Holmes. Naked.

Her breath hitches as she takes in the expanse of pale skin, the lean but nicely toned body. Licks her lips as she catches sight of his firm, _pert_ bum. She’s perfectly aware that pert isn’t usually ascribed to the male form but right now she can’t think of a better word.

She admires the play of shadows on his skin as he walks to the large bathtub, bends as he dips his fingers in to test the temperature. Obviously happy with it, he steps into the tub, sinking down almost immediately until only his head and neck are visible above the dense bubbles. She finds herself mirroring Sherlock’s moan of enjoyment – his is silent to her but she knows his velvet-smooth baritone well enough to imagine the sound – her own is but a whisper but oh so loud in the privacy of her office.

Andrea knows she should disconnect from the security feeds. That she’s crossing the line of acceptable. That she’s encroached too far already, although who would blame her for ogling at the infamous hat detective! The question of why Sherlock is in his brother’s house – his bathroom even – emerges from the confusion that is her current thoughts.

And it’s answered almost immediately.

This time she can’t hold back the gasp when she sees Mycroft Holmes approach his brother. Surprise with a small amount of relief that he’s covered by a dressing gown. Andrea finds herself asking more questions all of which she firmly pushes aside as she decides to disconnected _now_ when she catches a movement that makes her stop.

Sherlock raises a wet arm and hooks it around the back of his brother’s neck. He’s obviously pulling because Mycroft ducks and then they’re kissing.

Andrea is numb. She doesn’t know how to – in fact, can’t – react or even simply process what she’s seeing. Sherlock’s slim fingers drag through his brother’s own dark, short hair, leaving bubbles that glint on her screen. She thinks she caught a flash of tongue as they kiss.

It’s sexy, taboo and hot all at the same time. And she can’t tear her eyes away.

Doesn’t want to.

That seems very important to her.

Focussing back on her screen she finds that in the few minutes while she’s been questioning her own morality, her views on right and wrong, Mycroft has joined his brother in the bath. The camera is positioned in the back-left corner of the bathroom – discrete and near invisible – and with the brothers, Sherlock leaning back against Mycroft’s solid torso, facing east, her view is limited but good enough to see the tenderness on the elder’s face as he turns Sherlock’s head to the right for another deep, long kiss.

Andrea can’t tear her eyes away from the elegant and sensual image.

Sherlock breaks the kiss, she notes, but not before dropping a quick peck on his brother’s nose and she can’t help the giggle that bursts from her at the chagrined look on Mycroft’s face. Is enthralled as it melts into indulgence as Sherlock shifts in his arms – she can imagine the sound of water slapping the sides of the tub at the displacement – and rests his head on his brother’s shoulder.

She watches enraptured as Mycroft says something, head dipped so he’s talking directly into Sherlock’s ear. It’s immediately obvious that whatever he said is a teasing remark because Sherlock grabs a handful of bubbles with his right hand and targets Mycroft’s face. He doesn’t get his aim quite right as he’s laughing as he lobs. But the faux-affronted look on Mycroft is satisfying enough for both Sherlock and Andrea.

Andrea wonders what it says about her that she finds the image of Sherlock brushing away stray bubbles from Mycroft’s hair and face _cute_.

A movement catches her attention – of water lapping at the other end of the bathtub. The light ripples become more pronounced before her eyes – _interference and diffraction patterns_ her mind supplies. Her face heats up as she realises what sort of movement could cause that reaction. A glance at the other end of the tub confirms her suspicions.

The only hint from Mycroft is the flex of the muscles in his right arm. Sherlock’s hands are still not visible so she decides he must be holding onto Mycroft’s thighs to stop himself from slipping, probably supported by Mycroft’s other hand wrapped around his slim waist. The younger Holmes is squirming in his brother’s embrace – Andrea can only imagine the exquisite tease he must be experiencing – for teasing it must be if Sherlock’s face is any indication. His head is tipped back and so she can clearly see he has his eyes closed and he’s biting his lower lip, as though he’s trying to stop the gasps and moans from escaping without his consent.

She can pin-point the second when Sherlock’s control snaps. Can’t stop the shiver as she imagines the guttural groan the younger brother lets out.

When Sherlock suddenly pulls away from Mycroft, making an abortive movement Andrea can’t quite see, she’s confused. It quickly melts away when she notices the two men have switched positions – Sherlock is still in front but now they’re both facing in the other direction.

Sherlock is bent over the bathtub, long arms resting upon the tiles the cover the distance between the edge of the tub and the wall. Mycroft is tracing his fingers across his brother’s back in a possessive gesture, his face shines with so much desire, need and _love_ that it makes Andrea gasp. She realises he must be preparing his brother, which is quickly confirmed by Sherlock’s own flushed face and the way he moves his hips, grinds back into Mycroft.

If her feed had audio, Andrea wonders what she would hear. It’s clear from the images the two brothers are engaging in some form of verbal foreplay. She fancies Sherlock would be a stuttering mess at this very moment with his older brother, incongruous though it would have seemed to Andrea not even an hour ago, his voice rough with sex and desire telling Sherlock how beautiful he looked, how wanton.

The words would be dirty, coarse. Certainly nothing that she’d ever expected to spill from Mycroft’s mouth but now all she can do is imagine how he’s telling his brother how he’s going to fill him, how tight and exquisite his brother feels around his fingers, that perhaps he should let Sherlock fuck himself on his cock.

She’s also entirely convinced the elder Holmes would, at the same time, whisper how much he loves Sherlock, desires and needs him. Because it’s all too obvious to Andrea now. That they must hide it from the world is a given. But how effectively they deceive everyone around them given the heat and intensity between them is a surprise.

Andrea shifts and squirms. Flushes at the sudden realisation that she’s _wet_. She plants both her hands on her desk as she watches as Mycroft leans over Sherlock, is asking him something. When Sherlock nods and pulls Mycroft’s face down for a kiss – this time she can clearly see how wet, filthy and incendiary it is – she assumes he’s confirming that he’s ready.

Her breath catches as her eyes are fixed to her screen. Mycroft is just keeling there, one hand braced against the bathtub rim, the other holding onto Sherlock’s hip. From Sherlock’s expression, she realises Mycroft must be teasing him, drawing out the tension. Andrea realises she’s trembling – she can’t imagine how Sherlock is feeling at this moment.

It isn’t Mycroft’s shift in balance or position that confirm he’s breached Sherlock but the blissful expression on his face. Sherlock’s mouth, in turn, falls open and Andrea imagines she can hear his throaty moan as if they were in the same room. She’s gripped as Mycroft waits for some sort of signal from Sherlock before he moves again. It’s only because she’s concentrating so diligently that she notices the minute shift of Sherlock’s hips that sets the rest into motion.

The first thrust almost looks brutal and it’s clear it wrenches moans from both brothers. But there’s no hesitation, just the firm, rocking movements from Mycroft as Sherlock writhes and shakes under him.

Andrea can’t look away. She’s panting and now that Andrea is aware how turned on – and wet – she is, she realises that she’s probably ruined her panties and will need to make a trip to the dry cleaners. Her only saving grace is her skirt is black and will hide any stains.

The vision of the two brothers falling apart under each other’s touch is almost too much for her and she despairs. Her self-discipline shatters when Sherlock tilts his hips and does something that causes Mycroft to arch, drive himself into Sherlock with faster, sharper thrusts and Sherlock enthusiastically meets his every touch.

She drops her hand, lets her fingers trace a path up her thigh trailing a tingling feeling, until she reaches her panties. They’re soaking. Andrea slips a couple of fingers under the thin, soggy fabric and strokes herself. Her thumb quickly follows to circle her sensitive clit. She’s so wet her hand is slick in seconds.

Her eyes don’t move from her screen. The expressions on the brothers’ faces make it clear both men are clinging to the edge. Mycroft starts to look desperate, wrecked and it’s not long before he’s coming, his body grinding against Sherlock’s, as Andrea mentally adds the sensations of a cock spurting hot come into the tight, spasming body while she continues the rough, thrusting movements of her two fingers in her own cunt.

Sherlock turns around and perches on the bathroom tiles, legs spread. She imagines there’s a trail of come dripping out of him and trailing down the curve of the bathtub. Andrea can’t see Sherlock clearly anymore but she can see his arm move as he strokes himself, bringing himself off to come over Mycroft. She adjusts the speed of her thrusts to match Sherlock’s strokes of his cock. Makes sure to rub at her clit. Finds herself grinding her hips down on her fingers. She’s getting close.

Mycroft’s gaze is fixed on Sherlock’s groin, Andrea presumes, on Sherlock’s slim fingers circling and pulling at his own cock. He’s still panting, coming down. Andrea can’t see Sherlock’s face for the tell-tale sign he’s about to come, spill over his fingers and over Mycroft but she notices through her own haze of arousal and impending orgasm that Sherlock’s about to come. His body tenses for a moment, stills completely before he shudders. And comes.

Seconds later Andrea comes as well. She can’t hold back the low, keening moan as her muscles clench around her fingers and her entire body trembles and tingles with the force of her climax. Her hand is slick and she’s sure there’s probably a damp patch on her office chair.

With her clean hand, she quickly shuts down the surveillance, noting the brothers were having a shower as she disconnects and shuts her computer down. A quick glance at her chair as she rises to hurry to the Ladies to wash her hands and dry her wet pussy as best as she could given her state, confirms the damp spot.

She’ll need to handle that first thing in the morning she decides as she walks back to her office with clean, dry hands. Andrea _will not_ accept the idea of Mycroft deducing what she’s done, what she’s discovered and seen, from her office chair.

But first.

Andrea finds a particular name in her phone. Calls it. “Hi there,” she says when it connects. “Are you free tonight?” She grabs her handbag, carefully drops her damp panties into a side compartment. “Wonderful,” she replies. “Can I come over?” she asks.

There’s a wicked smile on her lips as she closes and locks her office behind her. “Oh _yes_ ,” she confirms. “Think you can keep up?”

**Author's Note:**

> I don't know what came over me ... this just happened.


End file.
